The present invention relates to a camera system and a recording medium.
In a conventionally-known camera system, a plurality of divisional images of an object are continuously photographed (hereinafter referred to as panoramic photography), and the divisional images are pasted to produce one continuous image (hereinafter referred to as a panoramic image). When a panoramic image is produced, if a plurality of images are simply pasted, the obtained panoramic image is unnatural and low in paste-up accuracy. To avoid this, an image synthesizing apparatus for producing a more. natural panoramic image by means of a cylindrical conversion process is proposed. In the cylindrical conversion process, pieces of divisional image information are projected on an imaginary cylindrical plane of a photographed image, so that a more natural panoramic image can be produced.
FIG. 2 is a diagram for explaining a basic principle of the cylindrical conversion process.
In FIG. 2, a reference symbol R denotes an object, and a reference symbol O denotes a reference point of a camera (in general, a nodal point of an optical system). Reference symbols Q and Qxe2x80x2 denote planes of projections on which an image of the object is projected when photographed. In this case, a cylinder P, the center of which coincides with the point O, is equivalent to a plane of projection when a panoramic image is photographed.
A plurality of images projected on the planes of projections Q and Qxe2x80x2 are converted to images projected on the cylinder P, and the adjacent converted images are pasted together.
For example, FIG. 3A shows photograph images projected on the planes of projections Q and Qxe2x80x2, and FIG. 3B shows images obtained by projecting. the photograph images on the cylinder P. When the images shown in FIG. 3B are synthesized by the conventional method, a panoramic image as shown in FIG. 3C is obtained.
FIG. 4 shows divisional images A, B and C obtained by photographing a linear object. When the divisional images A to C are simply synthesized, the resultant image is unnatural and nonlinear, as shown in FIG. 5. However, a natural image as shown in FIG. 6 can be obtained by the aforementioned cylindrical conversion process.
When images are pasted and synthesized to produce a panoramic image by the method described above, information on the angle of view of the camera is required in order to determine the diameter of the cylinder on which photographed images are projected. The information on the angle of view can be calculated from the focal distance of the camera and the size of the image pickup element. However, this matter is not known to people in general. Further, when an image is photographed by a camera with a zoom lens which has been widely used recently, only the longest and shortest focal lengths of the zoom lens can be known.
To overcome the above drawback, Japanese Patent Application No. 2871/98 discloses a method for calculating an angle of view from an overlapped region of two images pasted together.
FIGS. 7A and 7B are diagrams for explaining a cylindrical conversion process disclosed in Japanese Patent Application No. 2871/98. In the cylindrical conversion process, a plurality of images photographed in the angle of view xcex1x are converted to images projected on a cylindrical plane, as shown in the drawings. The coordinates of a point of an object projected on the cylinder are represented as (xcex8,Y)t in a cylindrical coordinates system and the coordinates of the point projected on a photograph plane are represented as (x,y)p. A point on the cylinder is represented by coordinates (X,Y)t, where X denotes a length along the cylindrical surface. When the unit of xcex8 is radian, X is equal to Rxc3x97xcex8(X=Rxc3x97xcex8).
Further, it is assumed that a reference point of the camera is )t, the origin on the sylindrical surface is C, the radius of the cylinder is R, the origin on the plane of projection on which a photographed image is projected is Op=(xcex80, 0)t, the width of the photographed image is Wx, and the angle of view xcex1x is an angle of view in the X dorection (between the center and the end of the image). In this case, the radius R of the cylinder is represented by the following equation (1).
R=Wx/(2xc2x7tan xcex1x)xe2x80x83xe2x80x83(1)
Further, the following relationship is established between (x,y)p and (xcex8,Y)t.
(x, y)p=(Rxc2x7tan(xcex8xe2x88x92xcex80), Y/cos(xcex8xe2x88x92xcex80))xe2x80x83xe2x80x83(2)
Based on these equations, (x,y)p is converted to (X,Y)t, so that an image is produced on the cylinder by projecting the photographed image thereon.
According to Japanese Patent Application No. 2871/98, information on the angle of view is obtained in the following manner. FIG. 7B hows a state in which a camera mounted on a tripod (not shown) continuously photographs images of an object, while rotating by an angle xcex2 relative to the object. The angle of view in the horizontal direction of the camera is xcex1x, and the size of the photographed image is Wxxc3x97Wy.
First, a part of the object included in both the adjacent images is selected as a characteristic point. The point in one image corresponding to the characteristic point in another image can be searched out by utilizing, for example, a method disclosed in Jpn. Pat. KOKAI Publication No. 6-141228.
It is assumed that the characteristic point is projected on the point (xcex8,Y)t on the cylinder, the origins of the two (left and right) images are OL=(xcex8L,0)t and OR=(xcex8R,0)t, and the coordinates of the characteristic point on the photographed images are (xL,yL)p and (xR,yR)p. In this case, the following relationship is established on the basis of the equation (2).
(xL, yL)p=(Rxc2x7tan(xcex8xe2x88x92xcex8L), Y/cos(xcex8xe2x88x92xcex8L))xe2x80x83xe2x80x83(3)
(xR, yR)p=(Rxc2x7tan(xcex8xe2x88x92xcex8R), Y/cos(xcex8xe2x88x92xcex8R))xe2x80x83xe2x80x83(4)
The following equation (5) is obtained from the equations (1), (3) and (4), so that the angle of view xcex1x is obtained.                               tan          ⁢                      xe2x80x83                    ⁢          α          ⁢                      xe2x80x83                    ⁢          x                =                                                            y                L                2                            -                              y                R                2                                                                                      y                  L                  2                                ·                                  A                  R                  2                                            -                                                y                  R                  2                                ·                                  A                  L                  2                                                                                        (        5        )            xe2x80x83AR=2xc2x7xR/Wx, AL=2xc2x7xL/Wx
At the same time, the difference in angle in the direction of the camera, xcex2=(xcex8xe2x88x92xcex8R)xe2x88x92(xcex8xe2x88x92xcex8L) is obtained by the following equations (6) and (7).                               tan          ⁡                      (                          θ              -                              θ                L                                      )                          =                                                            2                ·                                  x                  L                                                            W                x                                      ·            tan                    ⁢                      xe2x80x83                    ⁢                      α            x                                              (        6        )                                          tan          ⁡                      (                          θ              -                              θ                R                                      )                          =                                                            2                ·                                  x                  R                                                            W                x                                      ·            tan                    ⁢                      xe2x80x83                    ⁢                      α            x                                              (        7        )            
As described above, since the angle of view can be automatically obtained from images having overlapped regions, a choice of camera types used to produce a panoramic image can be increased. In the method described above, the angle of view xcex1x is obtained from the characteristic point and the corresponding point of the two adjacent images. However, if the angle of view is determined by the method of least square, using a greater number of points, influences of errors due to the search of the corresponding point or noises in images can be reduced.
However, the method for calculating the angle of view described in Japanese Patent Application No. 2871/98 has the following problems. Since the process of pasting two images is required, it takes a considerable time to calculate the angle of view. In addition, information on the angle of view cannot be accurate, since it is calculated in an estimate.
It is accordingly an object of the present invention to provide a camera system, which can calculate an angle of view quickly and accurately and produces a natural and accurate panoramic image.
To achieve the above object, according to a first aspect of the present invention, there is provided a camera system comprising:
a camera including a photographing device for photographing an object, and a recording medium for storing divisional images of the object photographed by the photographing device and information relating to an angle of view of photographing; and
a panoramic image synthesizing apparatus for performing a cylindrical conversion process based on the divisional images stored in the recording medium and the information relating to the angle of view, and synthesizing cylindrically converted images to produce a panoramic image.
According to a second aspect of the present invention there is provided a camera system comprising:
a camera including a photographing device for photographing an object, and a detachable recording medium for storing divisional images of the object photographed by the photographing device and information relating to an angle of view of photographing; and
a panoramic image synthesizing apparatus including: an image information reading section for reading the divisional images and the information relating to an angle of view of photographing stored in the recording medium loaded in the panoramic image synthesizing apparatus; an angle-of-view calculating section for calculating an angle of view of each of the divisional images using the information relating to an angle of view of photographing read by the image information reading section; a cylindrical conversion section for cylindrically converting each of the divisional images using the angle of view calculated by the angle-of-view calculating section; and an image synthesizing section for synthesizing the cylindrically converted divisional images converted by the cylindrical conversion section to produce a panoramic image.
According to a third aspect of the present invention, there is provided a computer-readable recording medium storing programs to cause a computer to execute a panoramic image synthesizing process comprising the steps of:
reading a plurality of images for constituting a panoramic image recorded in a camera and information relating to an angle of view of photographing in panoramic photography; and
synthesizing a panoramic image by a cylindrical conversion process based on the plurality of images for constituting a panoramic image and information relating to an angle of view of photographing in panoramic photography.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.